Rust inhibiting composition



Patented Dec. 25, 1951 RUST INHIBITING COMPOSITION Alfred B. Matuszak, Jersey City, and James W. Hand, J r., Summit, N. J assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application November 27, 1948, Serial No. 62,416

2 Claims.

This invention relates to rust preventing oil compositions and more particularly to mineral lubricating oil compositions which tend to inhibit rusting and corrosion of metal parts which are exposed to moisture.

A primary object of the present invention is the preparation of compositions which may be employed as internal combustion engine lubricants and which will also serve for the protection of exposed surfaces of such engines when the same are not in use. When operating engines in climates having a high humidity, rusting begins within a very short period of time after the engine is shut down. The compositions of the present invention are particularly valuable in preventing such rusting and they are valuable not only in the lubrication of internal combustioFengines, but with oil bases of suitable viscosity they may be employed as turbine oils or as lubricants for fire arms, ordnance equipment, industrial machinery, etc., and in tact for any lubricating purposes where metal surfaces are exposed to humid air.

It is known that partial esters of polyhydroxy alcohols are efiective rust inhibitors when employed as lubricating oil additives or as the principal components in slushing oils. It is also known that diamines show moderate rust inhibiting properties when employed in the presence of rust promoting acidic materials because 01' their acid neutralizing properties. It has been found in accordance with the present invention that when a partial ester of a polyhydroxy alcohol and a diamine are added to an oil base, the composition thus formed exhibits rust inhibiting effects superior to that obtained when either or the components is employed separately in the same base oil and substantially greater in amount than that which would be expected from the combined efiects of the two additives, and the efl'ects are obtained whether or not rust promoting acidic materials are prescut.

The partial esters of polyhydroxy alcohols which are employed in the compositions of the present invention are those which are derived from polyhydroxy alcohols containing not more than carbon atoms per molecule and aliphatic or cycloaliphatic monocarboxylic acids, saturated or unsaturated, straight chain or branched, containing from 6 to 30 carbon atoms per molecule, and which contain at least one free hydroxyl group.

Examples of the polyhydroxy alcohols which are to be employed in preparing the partial esters include ethylene glycol, diethylene glycol, glycerol, diglycerol, pentaglycerol, polyethylene glycols and polyglycerols containing not more than 20 carbon atoms per molecule, propylene glycol, 1,3-pr0panediol, pentaerythritol, sorbitan, sorbitol, inositol, dipentaerythritol, tetramethylolcyclopentanol, tetramethylolcyclohexanol, and anhydro-ennea-heptitol.

Carboxylic acids which are suitable for the partial esterification of the polyhydroxy alcohol include any aliphatic or cycloaliphatic monocarboxylic acid, saturated or unsaturated, straight chain or branched, having 6 to 30 carbon atoms per molecule. Among the more preferred examples of such acids may be mentioned caproic, caprylic, lauric, palmitic, stearic, oleic, linoleic, ricinoleic, oleomargic, erucic, behenic, arachidic, lignoceric, and similar fatty acids or mixtures thereof, also the naphthenic acids as well as the carboxylic acids derived by the oxidation of petroleum products or by the oxidation of oxygen-containing products prepared by the 0x0 process. Naturally occurring products containing any of the above or similar acids, such as tall oil, castor oil, soybean oil, linseed oil, olive oil, tung oil, rapeseed oil, menhaden oil, and the like, or acids derived therefrom, such as coconut fatty acids, may be conveniently employed.

The diamines which may be employed as one of the additives in accordance with this invention are those in which the two amino groups are attached to a hydrocarbon radical containing from 2 to 10 carbon atoms. These-include aliphatic, cycloaliphatic, and aromatic diamines and those in which short alkyl chains are attached to cycloaliphatic or aromatic nuclei. These diamines may be saturated or unsaturated. As examples of suitable diamines may be mentioned the following: ethylene diamine, propylene diamine, tetramethylene diamine (putrescine), hexamethylene diamine, octamethylene diamine, decamethylene diamine, 1,2-diaminocyclohexane, 1,3-diamino-cyclohexane, 1,4-diamino-cyclohexane, 1,3-diamino-l-methyl-cyclohexane, 1,1-dimethyl-3,5-diamino-cyclohexane. the phenylene diamines, the toluylene diamines. and the xylylene diamines.

For the purpose of the present invention the partial esters of polyhydroxy alcohols are added to the base stock in proportions from about 0.01% to 10% by weight (generally from 1% to 3%), and the diamine is added in proportions ranging from 0.001% to 5% by weight (generally from 0.05%

to 0.5%). In some cases larger proportions of additives than those specified may be employed to advantage.

Below will be described examples of the application of the present invention to a lubricant Employing a base oil consisting of a solven extracted Mid-Continent lubricating oil of 120' seconds viscosity Saybolt at 210 F., a number of blends were made by adding various additives or combinations of additives to this oil base. Two examples of partial esters of a polyhydroxy alcohol. viz., pentaerythritol mono-oleate' and sorbitan mono-oleate, and oneexample of a diamine, viz., propylene diamine, were employed, alone and in various combinations, for the purpose of showing the comparative effects of the additives when used alone and in combinations in accordance with the present invention.

The rust inhibiting properties of the various oil blends and of a sample of the base oil containing no additive were determined by using the same as a crankcase oil in a single cylinder air cooled engine of 5.7 H. P. at 2400 R. P. M. speed, manufactured by the Wisconsin Motor Corporation. The engine was operated on 91 grade aviation gasoline containing 4 cc. tetraethyl lead per gallon. After running the engine for eight hours with the test oil, the stainless steel cylinder, which has the same composition as the cylinders of a full scale airplane engine, such as a Pratt and Whitney R1340 engine, was removed and stored in a humidity cabinet in which the temperature was caused to vary between 72 and 90 F. and the relative humidity between 94% and 53% during each 24 hour period. Typical conditions in a tropical climate that are known to favor rapid rusting of aircraft engine cylinders were thus simulated. After each day the amount of rust present on the cylinder wall was observed and the storage period continued until a. test period of five days had been completed. Each oil sample was tested in this manner. The observations of the condition of the cylinder are given in the following table:

Cylinder rusting test [Per cent 0! cylinder wall rusted] Days of Storage Unhibited. Oil 5 l0 15 22 30 Same+l% pentraeryth ol monooleate 1 3 5 8 l0 Same+'l% sorbitun mono-oleatc. 4 6 9 l2 l4 Same+0.l% propylene diamine 5 6. 5 7. 5 9 l0 Same+l% pcntaerythritol monooleate+0.l% gropylene diamine 0 0. 25 0. 5 0. 5 0. 6 Same+l% sor itan mono-oleate+ 0.1% propylene diamine 2 2 2. 5 2. 5 3

It will be noted that the oil blends containing the combinations of ester and diamine possess considerably greater rust inhibiting properties than the blends containing either an ester or the diamine alone.

What is claimed is:

1. A mineral lubricating oil containing dissolved therein 0.01% to 10% of pentaerythritol mono-oleate and 0.001% to 5% of propylene diamine. I

2. A mineral lubricating oil containing dissolved therein about 1% of pentaerythritol mono-oleate and about 0.1% of propylene diamine.

ALFRED H. MATUSZAK. JAMES W. HAND, JR.

REFERENCES CITED The following references are of record in the 

1. A MINERAL LUBRICATING OIL CONTAINING DISSOLVED THEREIN 0.01% TO 10% OF PENTAERYTHRITOL MONO-OLEATE AND 0.001% TO 5% OF PROPYLENE DIAMINE. 